Installation for automatic polishing

ABSTRACT

An automatic polishing installation in which workpieces are advanced along a path to successive spaced polishing stations where the advancing travel is temporarily halted and the work pieces are each rotated about a respective axis perpendicular to the direction of advance. The workpieces and/or the polishing heads at the pollishing stations may also be moved along directions which are transverse to the direction of advance and to said axis of rotation so that the polishing heads cover the centre surface of the workpieces which usually have non-planar configuration. If desired, means may be incorporated for programming differently the various workpiece supports for accommondating several different shapes of workpiece.

United States Patent Plantevin et al. 1 June 3, 1975 541 INSTALLATION FOR AUTOMATIC 2.552.194 5/1951 Lindsay et a1 51/76 R 5,337,024 8/1967 Gilewski 51/76 R POLISHING inventors: Bruno Plantevin, Rueil; Jacques Touchard, Fontenay-le-Fleury, both of France Regie Nationale des Usines Renault, Billancourt, France Filed: Nov. 27, 1973 Appl. No.: 419,246

Assignee:

Foreign Application Priority Data Nov. 28, 1972 France 72.42268 Primary Examiner-Othell M. Simpson Attorney, Agent, or FirmStevens, Davis, Miller & Mosher [57] ABSTRACT An automatic polishing installation in which workpieces are advanced along a path to successive spaced polishing stations where the advancing travel is temporarily halted and the work pieces are each rotated about a respective axis perpendicular to the direction of advance. The workpieces and/or the polishing heads at the pollishing stations may also be moved along directions which are transverse to the direction of advance and to said axis of rotation so that the polishing heads cover the centre surface of the workpieces which usually have non-planar configuration. If desired, means may be incorporated for programming differently the various workpiece supports for accommondating several different shapes of workpiece.

6 Claims, 6 Drawing Figures INSTALLATION FOR AUTOMATIC POLISHING The present invention relates to an installation for automatic polishing.

Conventional automatic polishing systems pass the workpiece to be polished in front of a support for abrasive particles while ensuring a certain abrasive pressure on the workpiece, so as to remove very fine chips from the material to be polished. The abrasive may, for example, be supported by abrasive belts, discs provided with glued abrasive, discs provided with abrasives which are agglomerated by lubricants, or discs having abrasive incorporated therein.

The various assemblies which each comprise abrasive material on its support, such as abrasive belts or discs, are disposed on polishing heads.

So as to obtain the entire sequence of operations on an automatic machine, the polishing heads are arranged so as to operate successively on the workpiece to perform a progressively finer polishing, up to the desired degree of finish. This is carried out successively on the various zones of the workpiece, especially on top, underneath and in the middle.

When the workpieces to be polished have on their major dimensions portions which are straight or slightly curved and whose transverse section is approximately constant, the automatic polishing machine causes such workpieces to move translatorily past a succession of polishing heads placed side-by-side. The route of displacement of the items may have the form of a straight line with loading and unloading performed at the two opposite ends of the line, with the workpiece supports returning empty from the unloading station to the loading station.

This arrangement is more particularly obtained by mounting the workpiece supports on an endless chain which is guided on and driven continuously by two sprockets disposed at the two opposite ends of the installation. These machines may also be of the out-andreturn type and comprise a guidance member for the supports of the workpiece, having two parallel, straight lines out and back, along which lines the polishing heads are sequentially disposed.

In the latter case loading and unloading will take place at one and the same end.

In practice, it happens that workpieces other than those which comprise an approximately rectilinear portion are to be polished, but additionally the workpieces may have turned down ends which form an approximate right angle with the rectilinear portion, especially in the case of motorcar bumpers.

In this latter case the translatory machines such as those which have been defined above do not enable the ends to be polished and this requires expensive finishing by manual polishing. In order to overcome this problem a special section for effecting the polishing of the ends has been inserted into the route of their movement. This frequently employed method consists in causing the pieces to pivot about an angle of 90 by means disposed near the driving member for the endless chain. In this section of the machine the front faces are thus perpendicular to the axis of their advance and the turned down ends become parallel to this axis. It is then sufficient to place an adequate number of polishing heads at either side of the pieces so as to obtain a degree of polishing similar to that obtained on the front portions of great length. At the end of this section the pieces undergo a further rotary movement about an angle of in the reverse sense to return them to their original orientation.

However, this arrangement has a disadvantage because, if the desired degree of polishing according to the simple workpiece" case necessitates movement past N polishing heads, then completing the entire gamut of operations on workpieces with turned down ends requires N polishing heads for the straight length representing the main face. N polishing heads for one end of each piece, and a further N polishing heads for the other end of each piece. It is thus apparent that the number of polishing heads has been trebled relative to that which is necessary for any given face.

Furthermore, the supplementary polishing heads for polishing of the endswork only during a very brief fraction of time.

For example, when the front face has a length of l .70 m and the ends have a length of 0.50 m, each end polishing head works during less than one-third of the time. 0

Furthermore the working stations are such that the operators must remove and position the workpieces with respect to their support members while the supports are in motion and this results in fatigue and in lack of safety of the polishing station.

Such a procedure, which is satisfactory from the point of view of the results obtained, requires major investment in material, a large occupied floor space, and presents disadvantageous conditions for the personnel.

It is an object of the present invention to obviate these disadvantages and to permit all the workpieces to be polished with a single series of N polishing heads with resulting saving of capital and floor space occupied.

According to the present invention there is provided an installation for polishing workpieces, comprising workpiece support members integral with a linear drive element and arranged at specific intervals along the drive element, means for driving said drive element in step by step manner to bring the various pairs of sup port members to face stationary polishing stations, and means for pivoting each of the workpiece support members about an axis which is perpendicular to the direction of advance of the drive element and intersects the longitudinal axis of the drive element.

In the installation according to the invention each machined workpiece, more particularly bumpers of automotive vehicles, moves so that the entire surface to be treated from one end to the other is moved past each polishing tool of the machine.

Such a machine is particularly advantageous by virtue of the very favourable utilisation of the expensive polishing heads which, apart from during the short duration indexing movements of the drive element, never remain partially inactive. Working conditions are also improved by the stepwise operation and the fixing of the workpiece can be more secure since loading and unloading are effected at standstill.

Moreover, a preferred form of the invention uses two polishing heads in opposition at each polishing station and this allows balance of the working forces.

Finally, with such an installation it is relatively simple to process different shaped pieces at the same time on the same chain.

In order that the present invention may more readily be understood the following description is given,

merely by way of example, of several embodiments. Reference will be made to the accompanying drawings in which:

FIG. I is a plan view of a polishing installation according to the invention;

FIG. 2 is a side view of the same installation illustrating an under-floor return route for loaded workpiece supports;

FIG. 3 is a top plan view from above of one embodiment of a device for driving a pair of workpiece support members for movements of both rotation and transla tion;

FIG. 4 is an elevational view along the arrow IV of FIG. 3;

FIG. 5 is an underneath plan view of a further embodiment of the device for rotatingly driving a pair of support members; and

FIG. 6 is an elevational view along the arrow VI of FIG. 4.

ln FIGS. I and 2 there is shown a polishing installation according to the invention which comprises a lin ear drive element comprising an endless chain 1 mounted on two sprockets 2, 2a at least one of which is powered so as to ensure the movement of the chain 1 in a vertical plane from right to left of the FIG., according to the arrow F. In the embodiment according to the invention the axes x x and y y, of the sprockets are horizontal but it is obvious that any other arrange ment could be adopted.

The drive element is arranged to have a return route underneath the floor 12 for the loaded support members to follow as they return to the sprocket 2a at the loading station end of the chain system.

To either side of the chain 1 and connected thereto are support members 4, 4a for carrying workpieces 5, 5a to be polished such as automotive vehicle bumpers having a rectilinear portion 6 which turned down ends 7, 70 at an angle of substantially 90 with the rectilinear portion 6. The support members 4, 4a are arranged in spaced pairs and each pair is mounted on the chain by a device 8 which is schematically shown in the drawing and is capable of permitting various displacements of the support members relative to the chain 1.

At either side of each pair of support members 4, 4a are stationary polishing stations 9, 9a each comprising a polishing head 10, 10a having an abrasive portion which is intended to come into contact with the pieces 5, 5a.

The polishing stations 9, 9a which number ten in the illustrated embodiment, are also arranged in pairs so as to face the pairs of support members.

A loading and/or unloading station 11 at the starting" end of the array of polishing stations does not itself include polishing stations However. this loading and/0r unloading station could equally well be situated at the finish" end of the array of polishing stations.

The installation according to the invention works follows:

The chain 1 advances step by step following the arrow F, past the polishing stations 9, 9a in such manner that the pieces 5, 5a are transferred from one working station to the next one to undergo successive polishing operations at the various stations and thus to obtain progressively an ever finer polish.

At each stop period in front of the stations 9, 9a the pair of support members 4, 4a is driven to rotate through an angle of at least I80, in the sense of the arrow F in a horizontal plane about a vertical axis a a, perpendicular to the direction of movement of the chain 1 and situated in a plane containing the longitudinal axis of the machine. Thus each workpiece 5 can be presented in its entirety to the polishing heads 10, 10a of the polishing stations.

In the present embodiment, which comprises ten polishing stations, each of the workpieces 5 is thus subjected to ten polishing operations during only five work steps.

The opposed position of the polishing heads 10, 10a makes it possible to balance the forces of the polishing heads during processing of the workpieces.

No polishing stations are provided on the lower return run of the chain (FIG. 2) but of course it would be possible, if desired, to accomplish a succession of complementary operations during this return period.

The advancing work of the actual polishing may be effected by moving the workpiece 5 in front of the polishing head 10 which can be considered as stationary, since the slight oscillations of the polishing head can be neglected for the purposes of this explanation. In this case the workpiece support 4 performs a copying movement of the piece in question, which may consist ofa rotary movement about a vertical axis and a translatory, horizontal movement of the same axis along the chain route, so as to keep the workpiece 5 in contact with the polishing head 10 (FIG. 3).

In a further embodiment the workpiece carrier 4 may be made to effect a simple rotation, the approach of the workpiece to the polisher being effected by a movement of each polishing head along the arrow F (FIG. 5).

These movements, both of rotation and of shifting, may be obtained in accordance with various known techniques such as by electric motors, or pneumatic or hydraulic jacks, and using conventional control means such as cams, contactors, or digital control systems which are also well known and do not form part of the present invention.

Although a workpiece 5 having a rectilinear portion and turned down ends has been described, it is evident that any general shape, bent to a greater or lesser extent can be polished by virtue of the respective workpiece polisher copying movements on the form of the workpiece by any adequate known means such as for example an appropriate cam.

Such an installation permits equally well both rapid repeat" work where identical pieces are polished at all the stations, as it does the polishing of different shaped pieces where each piece carrier is capable of performing the copying movement corresponding to the particular configuration of the piece which it carries. In the latter case the type of copying movement required may be selected, for example, at the loading station by inser tion of a cam or other programming means appropriate to the workpiece where the installation is controlled by the digital control device.

In FIGS. 3 and 4 there is shown one embodiment of a device for driving a pair of support members for both rotational and translational movement, such as has been described above when the polishing station is stationary and only the single rotary polishing head 10 is driven.

The support members 4, 40 holding bumpers 5, 5a essentially comprise a table 4.1 carrying a pair of planar elements 4.2 of substantially triangular form having an edge which is engaged in the central groove of the bumper 5, 5a. This edge of the element 4.2 is provided with an expansible member known per se which is actuated while the support table 4.1 is disposed on the active portion of the path of the chain 1 and consequently ensures the effective positional constraint of the bumpers.

At its lower portion the table 4.1 is extended by two diametrically opposed trunnions 13, 14 situated at the periphery of the table 4.1. The free end of trunnion 13 is engaged in and capable of moving in an elongate opening 15 extending longitudinally of an intermediate plate 16 of rectangular shape. The free end of the trunnion 14 passes freely through an elongate opening 17 disposed in the intermediate plate 16 symmetrical with respect to the opening 15 (FIG. 3).

The table 4.1 rests on a raised portion 16a of the intermediate plate 16 and it is capable of moving with respect to the plate 16.

The free end of the trunnion 14 is engaged and locked in an ellipsoidal groove 18 of a second, lower table 19, of a form identical to that of the table 4.1, and which rotatably supports an underneath profiled portion 16b of the intermediate plate 16. The intermediate plate 16, as well as a pinion 20, are keyed to a common shaft 21 capable of being driven by a pinion 22 fast on a shaft 23 of a motor 24. The bottom table 19 is driven for rotation in the reverse sense relative to that of the shaft 21 and intermediate plate 16 (by means not shown) so that by the time the intermediate plate has rotated through approximately 45 the orientation of the bottom table 19 relative thereto will have changed by 90 to withdraw the bumper to its position corresponding to engagement of the fixed axis polishing head 10 with the protruding corner of the bumper 5.

This effect may equally well be achieved by driving the bottom table in the same direction of rotation as the intermediate plate 16 but at three times its rate of rotation. Alternatively the bottom table 19 could be held stationary and the ellipsoidal groove replaced by one of a more complex form. The motor 24 is mounted for movement along a vertical axis z z,, such that when the support members 4 arrive at the level of the working station the pinion 22 rises to engage the pinion and does not disengage from the latter until the polishing operation has been terminated and further indexing movement is required.

In operation, a pair of bumpers 5, 5a supported by the table 4.1 and the elements 4.2 arrives at the level ofa work station and consequently of a motor 24. The polishing head 10 is fixed and actuated only for a rotary movement of its abrasive element. As earlier described, the motor 24 moves upwardly along the axis 2 z, 50 that the pinion 22 engages the pinion 20 to drive the shaft 2] and the intermediate plate 16.

The upper plate 4.1 is also driven since the table 4.1 is rendered integral with the plate 16 by the trunnion 13 engaged and locked in the elongate opening 15.

During the course of this movement the trunnion 14 which is guided in the ellipsoidal groove 18 moves according to the profile of said groove, which determines a complex predetermined movement of the plate 4.1 and the supports 4.2 which move laterally and rotate, the said movement being allowed by the elongate openings 15 and 17 provided in the rotating plate 16.

When the operation has been terminated the motor 24 again descends whereby the pinion 20 is freed and the device is uncoupled.

FlGS. 5 and 6 are views ofa further embodiment of a device for driving supports and bumpers in the case when twin. opposed polishing heads 10, are capable of a movement of translation along arrows P, which enables the rotary abrasive portions to be brought into contact with the workpiece to be polished.

As in the preceding case, the bumpers 5, 5a are mounted on planar elements 4.2 of triangular shape which are fixed on a table 4.1.

The device is in this case very simplified since the translatory movement is furnished by the polisher 10 according to the arrow F The table 4.1 is driven only for rotational movement which is transmitted to the table by the motor 24 by means of pinions 20, 22.

Various modifications may, of course, be made by the person skilled in the art to the devices and methods which have been described solely by way of nonlimiting examples, without departing from the scope of the invention as defined in the claims.

We claim:

1. An installation for polishing workpieces comprismg means for supporting a pair of laterally spaced workpieces to be polished, means for advancing said workpiece supporting means in step by step manner along a work path comprising two spaced sprockets, a sprocket chain looped thereabout and means for driving the chain for circulating movement about the sprockets,

loading and unloading stations disposed at an end of said chain loop,

polishing stations spaced along the work path and comprising a pair of polishing heads disposed in opposed relation laterally of said work path symmetrically about the plane which includes said axis of workpiece rotation and said work path direction, and

means for rotating said workpiece support means at least about an axis perpendicular to the direction of travel of the said chain.

2. An apparatus for polishing workpieces comprising spaced sprocket wheels, a sprocket change operatively looped about the sprocket wheels, pairs of means for polishing said workpieces spaced longitudinally along one reach of the looped chain with one member of each pair on one side of the chain and the other member of the pair on the opposite side of the chain, means for supporting a pair of workpieces in operative association with the polishing means at spaced points along said chain, means for driving the chain intermittently and stopping the chain with a pair of support means between each of said pairs of polishing means and with the workpieces carried thereby disposed in operative association with the polishing means, and means for rotating said support means about an axis perpendicular to the direction of travel of said chain and to thereby rotate the workpiece 180.

3. The polishing installation of claim 1 comprising means for simultaneously rotating and moving said support means with respect to a polishing head to maintain contact of the workpiece as the support means rotates.

4. A polishing installation as set forth in claim 3, wherein said workpiece support means are additionally mounted for movement perpendicular to said axis of rotation and said work path direction at the polishing stations, and including means operable simultaneously with operation of said selectively operable drive means for driving said workpiece support means for said perpendicular additional movement.

5. A polishing installation as set forth in claim l, wherein said workpiece support means comprise a pair of support members, a first table to which said support members are secured, an intermediate plate which supports said first table, two elongate openings extending along a common diameter of said intermediate plate, two trunnions extending from said first table and fixed thereto on a diameter thereof, a second table disposed below said intermediate plate, an elliptical groove formed in said second table, a shaft extending through said intermediate plate and said second table, means securing said intermediate plate non-rotatably with respect to said shaft, a pinion non-rotatably connected to said shaft, a second pinion adapted to be selectively engaged by the first mentioned pinion, and motor means drivingly connected to said second pinion, one of said trunnions being held captive in one of the elongate openings of the intermediate plate and the other trunnion being arranged to pass through the other opening of the intermediate plate to engage in said elliptical groove.

6. A polishing installation as set forth in claim 5, wherein said support means comprise a table, support members secured to said table, a shaft extending through said table, means keying said shaft to said table, a pinion keyed to said shaft, a second pinion, a motor drivingly connected to said second pinion, and means mounting said motor and said second pinion for movement along an axis parallel to that of said shaft, 

1. An installation for polishing workpieces comprising means for supporting a pair of laterally spaced workpieces to be polished, means for advancing said workpiece supporting means in step by step manner along a work path comprising two spaced sprockets, a sprocket chain looped thereabout and means for driving the chain for circulating movement about the sprockets, loading and unloading stations disposed at an end of said chain loop, polishing stations spaced along the work path and comprising a pair of polishing heads disposed in opposed relation laTerally of said work path symmetrically about the plane which includes said axis of workpiece rotation and said work path direction, and means for rotating said workpiece support means at least 180* about an axis perpendicular to the direction of travel of the said chain.
 1. An installation for polishing workpieces comprising means for supporting a pair of laterally spaced workpieces to be polished, means for advancing said workpiece supporting means in step by step manner along a work path comprising two spaced sprockets, a sprocket chain looped thereabout and means for driving the chain for circulating movement about the sprockets, loading and unloading stations disposed at an end of said chain loop, polishing stations spaced along the work path and comprising a pair of polishing heads disposed in opposed relation laTerally of said work path symmetrically about the plane which includes said axis of workpiece rotation and said work path direction, and means for rotating said workpiece support means at least 180* about an axis perpendicular to the direction of travel of the said chain.
 2. An apparatus for polishing workpieces comprising spaced sprocket wheels, a sprocket change operatively looped about the sprocket wheels, pairs of means for polishing said workpieces spaced longitudinally along one reach of the looped chain with one member of each pair on one side of the chain and the other member of the pair on the opposite side of the chain, means for supporting a pair of workpieces in operative association with the polishing means at spaced points along said chain, means for driving the chain intermittently and stopping the chain with a pair of support means between each of said pairs of polishing means and with the workpieces carried thereby disposed in operative association with the polishing means, and means for rotating said support means about an axis perpendicular to the direction of travel of said chain and to thereby rotate the workpiece 180*.
 3. The polishing installation of claim 1 comprising means for simultaneously rotating and moving said support means with respect to a polishing head to maintain contact of the workpiece as the support means rotates.
 4. A polishing installation as set forth in claim 3, wherein said workpiece support means are additionally mounted for movement perpendicular to said axis of rotation and said work path direction at the polishing stations, and including means operable simultaneously with operation of said selectively operable drive means for driving said workpiece support means for said perpendicular additional movement.
 5. A polishing installation as set forth in claim 1, wherein said workpiece support means comprise a pair of support members, a first table to which said support members are secured, an intermediate plate which supports said first table, two elongate openings extending along a common diameter of said intermediate plate, two trunnions extending from said first table and fixed thereto on a diameter thereof, a second table disposed below said intermediate plate, an elliptical groove formed in said second table, a shaft extending through said intermediate plate and said second table, means securing said intermediate plate non-rotatably with respect to said shaft, a pinion non-rotatably connected to said shaft, a second pinion adapted to be selectively engaged by the first mentioned pinion, and motor means drivingly connected to said second pinion, one of said trunnions being held captive in one of the elongate openings of the intermediate plate and the other trunnion being arranged to pass through the other opening of the intermediate plate to engage in said elliptical groove. 